Glycol systems should be checked at least once a year to ensure the system pH levels have not dropped below recommended levels. Glycol in general is acidic. The inhibitors that are added to them help neutralize the system pH, and help protect the system components. As the system ages, the inhibitors break down, causing the system pH to drop. At this point more inhibitors should be added to the radiant floor heating and snow melt systems. The system will reach a point where it will require a complete flush and re-fill. This is usually around 5-7 years, but will depend on the glycol used.